It is well known that streamlining the undercarriage of a long vehicle such as a trailer truck or straight van truck will reduce the aerodynamic resistance of a moving vehicle and thus save fuel. However, streamlining the undercarriage of a long vehicle such as a semi-trailer is impractical because integrated enclosures are heavy, costly, easily damaged, interfere with standardized structural design, and prevent access to parts and equipment underneath the vehicle. Consequently, removable attachments have been designed to streamline the undercarriage of long vehicles. However, past designs for removable attachments have not achieved significant utilization because they are typically easily damaged, difficult to repair, difficult to mount, incompatible with different trailer and truck geometries, become filled with snow and ice in winter driving conditions, do not provide the maximum drag decrease possible, and are too costly to generate a significant return on investment through associated fuel use reductions.
The device described herein seeks to improve on the prior art and past designs by using new aerodynamic geometry to provide improved drag reduction and by incorporating the capability for both vertical and lateral movement of the flexible flat panel airfoils in order to provide greater durability and impact resistance.
Prototypes of the device reduced a semi-trailer's fuel consumption by 7.45% in fuel economy tests conducted by a respected third party using the Society of Automotive Engineer's (SAE) J1321 type II standardized procedure. Past designs for comparable aerodynamic attachments have demonstrated a 4% to 6% reduction in fuel consumption in similar tests. The improved aerodynamic performance of the device described herein when compared to past designs is primarily due to the flexible design which allows for lower effective aerodynamic coverage to the ground. Wind tunnel tests on undercarriage aerodynamic attachments have demonstrated that a maximum drag reduction is achieved by enclosing the entire undercarriage from the bottom of the vehicle to the ground. This maximum drag reduction is due to preventing air flow from going underneath the attachment and impacting the wheels and axle components. However, enclosing the entire undercarriage with an aerodynamic attachment is impractical because uneven road surfaces such as rail-road crossings and inclined loading docks will impact the attachment when the vehicle moves over them causing damage to the device. Consequently, past designs typically demonstrate a ground clearance from level ground to the bottom of the attachment of 12 to 18 inches so that they can pass over irregular ground surfaces without being damaged. The device described herein achieves a much lower ground clearance than past designs of approximately 8 inches and therefore provides enhanced drag reduction while also improving operational effectiveness though the ability to absorb ground impacts. The low ground clearance of the device is made possible by incorporating a combination of flexible flat panels, articulating mounting brackets and flexible struts that enable the panels to easily deflect and curve. Because the device is constructed of durable and flexible materials and has numerous degrees of freedom of movement, it can bend to absorb impacts from the ground or absorb side impacts such as frozen snow banks, and can return to its original position. Prototypes have demonstrated the ability to flex up to 25 inches off the ground and return to their original position undamaged. Due to this flexibility, the device can pass over larger obstacles than past designs without damage. Many past designs have incorporated a flexible bottom panel section, but these designs do not provide the needed rigidity for lower panel aerodynamic resistance or add cost, weight and complexity to the design when still only providing clearance of up to 12 to 18 inches. This amount of clearance is not preferable as there are many operation situations where up to 20 inches of clearance is required for a typical semi-trailer. Unlike past designs which are mounted straight along the longitudinal edge of the vehicle, the device described herein also features an angled mounting position. This optimal aerodynamic positioning improves drag reduction on the wheel and axle components by diverting air flow around the outside of the vehicle preventing it from entering the space behind the attachment. The angled position also integrates with common vehicle features such as landing struts. Unlike past designs, the optimal aerodynamic positioning of this device also insures the panel does not interfere with operating the landing strut deployment hand crank mechanism. The angled position also removes the forward portion of the attachment from the sides of the vehicle, providing increased clearance to potential side impacts, further allowing unobstructed access to common vehicle features such as turn signal lamps. The device described herein is easily packaged and shipped, can be easily mounted on the undercarriage of trailers and trucks of different geometries and construction, resists damage, and can be easily repaired with replacement parts. The device described herein does not enclose the undercarriage of the trailer or create irregular surfaces, thereby preventing snow and ice build-up and allowing access to parts underneath the trailer or truck.
Despite a compelling need in the transportation industry to reduce fuel cost, prior art and past designs have been ineffective in providing a cost effective solution for most applications. The device described herein uses a minimal amount of material resulting in reduced weight and production costs. As every pound of weight of the device corresponds to less paid cargo capacity of the transportation vehicle, the device described herein weighs an approximate 175 pounds. The device described herein achieves many improved benefits due to its utilization of common, extruded flat panel plastic material. Extruded plastic panels offers ideal flex characteristics and considerable cost savings during manufacturing including both the production of the material as well as the ease of automated computer numerical controlled (CNC) fabrication of panel shapes and fastening holes. Other previous designs are limited by more expensive and complex designs using thermoplastic material that needs vacuum forming or injection molding. Other designs and prior art necessitate the use of multiple materials in the panel assembly or materials such as metal sheet, metal composite panels, or fiberglass composite panels that do not have the proper flex characteristics to effectively resist damage. The device described herein combines a new application of extruded plastic flat panel sheets with a new design method that enables the device to achieve efficiencies previously not possible.